Input: green crank of length L1.

Blue pulley of radius R1 is stationary.

Yellow pulley of radius R2 is fixed to yellow bar of length L2.

R1 = 2.R2

L1 = L2

A point on revolution joint of the yellow bar traces a straight line. Its lenght is 4.L1.

This mechanism has a relation with Cardano cycles.

If L1 ≠ L2, condition to get the said straight line: R1/R2 = 1 + (L1/L2)

The belt should be toothed.

It is possible to use chain drive instead of belt one.